1. Field of the Invention
The present invention generally relates to a motor's stator unit and, more particularly, to a motor's stator unit that can be coupled with a rotor or an impeller to construct a motor or a cooling fan.
2. Description of the Related Art
Conventionally, a motor or a cooling fan includes a base. A shaft tube is arranged on a center of the base. At least one bearing is installed in the shaft tube, so that a rotor is able to rotatably couple with the bearing. The conventional motor or the cooling fan further includes a stator having a silicon steel plate unit that is press fit around the shaft tube to prevent the stator from disengaging from the shaft tube.
Since the silicon steel plate unit is made of metal material, the silicon steel plate unit may excessively compress the shaft tube when fit around the shaft tube by press fitting. This may cause deformation of the shaft tube. The deformed shaft tube may further compress the bearing and therefore can damage or deform the bearing. As a result, the service life of the motor or the cooling fan is shortened.
Referring to FIG. 1, a modified fixed bearing structure of a DC fan is disclosed by Taiwan Patent No. 519259. The conventional fixed bearing structure 8 includes a base 81 and a shaft seat 82 arranged on a center of the base 81. The shaft seat 82 has an annular groove 821. The upper part of the shaft seat 82 is separated into an inner annular wall 822 and an outer annular wall 823 by the annular groove 821. A stator unit 83 is press fit around the outer annular wall 823. A retaining ring 84 is installed in the annular groove 821 to support the stator unit 83 and to prevent disengagement of the stator unit 83.
In the modified fixed bearing structure described above, the structure is of high complexity due to the formation process of the inner and outer annular walls 822, 823 and the installation process of the retaining ring 84, resulting in an inconvenient assembly.
Referring to FIG. 2, Taiwan Patent No. M284196 discloses a conventional cooling fan 9 comprising a fan frame 91, a bearing 92 and a stator 93. A central column 911 is arranged on a center of the fan frame 91. The bearing 92 is received in the central column 911. Threads 912 are arranged on upper and lower parts of an outer circumferential wall of the central column 911. The stator 93 may be fitted around the central column 911. The stator 93 includes an upper insulation sleeve 931 screwed to the thread 912 on the upper part of the central column 911, as well as an lower insulation sleeve 932 screwed to the thread 912 on the lower part of the central column 911. This structure provides enhanced coupling between the stator 93 and the central column 911.
Disadvantageously, not only does it require forming the threads 912 on the upper and lower parts of the outer circumferential wall of the central column 911, but it also requires forming another two threads on inner circumferential walls of the upper insulation sleeve 931 and the lower insulation sleeve 932 that can be engaged with the threads 912 of the central column 911. As a result, it is inconvenient to manufacture the cooling fan. In addition, it is also required to screw the upper insulation sleeve 931 and the lower insulation sleeve 932 to the central column 911, leading to an inconvenient assembly.